JP6049484B2 - Image heating device - Google Patents

Description

  The present invention relates to an image heating apparatus that thermally adjusts the surface of a rotating body by bringing a belt member into contact with the rotating body, and more specifically, a plurality of supporting rotating bodies that stretch the belt member are rotated by forming a twist angle. The present invention relates to a structure for copying a belt member on a curved surface of a body.

  An image forming apparatus that transfers a toner image carried on an image carrier onto a recording material, and heats and presses the recording material onto which the toner image has been transferred by a fixing device, which is an example of an image heating device, to fix the image on the recording material. Widely used. The image heating apparatus heats the recording material by sandwiching and conveying the recording material at a nip portion of a pair of rotating bodies (belt member or roller member) provided with a heating unit at least one.

  In recent years, with an increase in the speed of heat treatment of recording materials and an increase in the types of recording materials to be handled, heating of the rotating body by heating means alone decreases the surface temperature of the rotating body, making it impossible to achieve sufficient recording material heating performance. A case has occurred. For this reason, an image heating apparatus has been proposed in which a separately heated belt member is brought into contact with the curved surface of the rotating body whose temperature has decreased in contact with the recording material to ensure the necessary surface temperature of the rotating body ( Patent Documents 1 and 2).

  In Patent Document 1, an external heating belt, which is an example of a belt member, stretched around three supporting rotating bodies is brought into contact with a circumferential surface of a fixing roller, which is an example of a rotating body. In Patent Document 2, an external heating belt stretched between two supporting rotating bodies is brought into contact with the circumferential surface of the fixing roller. The first holding portion that rotatably holds one end portion of the two support rotating bodies and the second holding portion that rotatably holds the other end portion are individually supported by a common support member. Therefore, relative rotation is possible so as to form a twist angle between the two supporting rotating bodies.

JP 2004-198659 A JP 2007-2112896 A

  The position of the belt member in the direction along the support rotator is normally regulated by a rib formed on the support rotator or a rib formed on the belt member. However, the restriction by the ribs and ribs may cause unnecessary stress on the belt member and impair the life. Therefore, the steering control that dynamically adjusts the shift of the belt member along the support rotating body by rotating the support member so as to form an intersection angle between the bus line of the belt member and the bus bar of the rotating body. was suggested. When the belt member is brought into contact with the curved surface of the rotating body, a belt member is formed even if the bus bar of the rotating body and the bus bar of the belt member are not parallel by forming a twist angle between the two supporting rotating bodies. Can be brought into contact with the circumferential surface of the rotating body with a uniform applied pressure.

  However, in this case, when the belt member is assembled and replaced, workability is impaired if an unlimited twist angle is formed between the two support rotating bodies. If an excessive twist angle is formed, unnecessary force may be applied to the two supporting rotating bodies and their bearing structures.

  An object of the present invention is to provide an image heating apparatus that is excellent in workability when assembling and exchanging a belt member, and that does not apply unnecessary force to the two supporting rotating bodies and the bearing structure during the work. .

  The image heating apparatus of the present invention includes a rotating body that rotates in contact with a recording material, a belt member that rotates in contact with the fixing roller 101 in order to perform thermal adjustment of the fixing roller 101, and the belt member. A plurality of support rotators to be supported in a suspended manner, a first holding portion for rotatably holding one end portion of the plurality of support rotators, and a first support portion for rotatably holding the other end portions of the plurality of support rotators. Two holding portions, a supporting member that rotatably supports the first holding portion and the second holding portion so as to form a twist angle in the plurality of supporting rotating bodies, and a bus bar of the belt member A shift movement control mechanism that controls the shift movement of the belt member along the plurality of support rotating bodies by rotating the support member so as to form an intersection angle between the fixing roller 101 and the bus of the fixing roller 101; Maximum relative rotation of the first holding part and the second holding part A canonical structures for the degree put limits to a predetermined angle not any more relative rotation, but with a.

  In the image heating apparatus of the present invention, the limit structure restricts the maximum relative rotation angle of the first holding part and the second holding part to a predetermined angle, so that the workability is excellent when the belt member is assembled and replaced. Since relative rotation beyond a predetermined angle is impossible, relative rotation beyond a predetermined angle occurs, and unnecessary force is not applied to a plurality of support rotating bodies and their bearing structures.

1 is an explanatory diagram of a configuration of an image forming apparatus. FIG. 3 is an explanatory diagram of a configuration of a fixing device according to the first exemplary embodiment. It is explanatory drawing of the contact-and-separation mechanism of an external heating belt. It is explanatory drawing of the rotation mechanism of a holding frame. It is explanatory drawing of the crossing angle of the bus of a fixing roller, and the bus of an external heating belt. It is explanatory drawing of the cancellation effect of the applied pressure difference by a twist angle. It is explanatory drawing of the steering mechanism of an external heating belt. It is explanatory drawing of the drive part of a steering mechanism. It is an enlarged view of the drive part of a steering mechanism. It is explanatory drawing of arrangement | positioning of a belt deviation | shift amount detection sensor. It is explanatory drawing of the relationship between a belt shift direction and the rotation direction of a sensor flag. It is explanatory drawing of the fixing apparatus of a comparative example. It is explanatory drawing of arrangement | positioning of the control part in Example 1. FIG. It is explanatory drawing of operation | movement of a holding | maintenance frame. It is a perspective view of a control part. It is explanatory drawing of operation | movement of a control part. It is explanatory drawing of the relative rotation angle of a holding frame. It is explanatory drawing of the control angle of the relative rotation of a holding frame. It is explanatory drawing of the effect of Example 1. FIG. It is explanatory drawing of arrangement | positioning of the control part in Example 2. FIG. 6 is an explanatory diagram of the thermistor arrangement in Embodiment 2. FIG. It is explanatory drawing of the rotation stop structure of the sensor support shaft with respect to a holding frame. It is explanatory drawing at the time of relative rotation of a holding | maintenance frame. It is explanatory drawing of operation | movement of the control part in Example 2. FIG. It is explanatory drawing of the control part of Example 3. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Image forming apparatus>
FIG. 1 is an explanatory diagram of the configuration of the image forming apparatus. As shown in FIG. 1, the image forming apparatus 100 is a tandem intermediate transfer type full-color printer in which yellow, magenta, cyan, and black image forming portions Pa, Pb, Pc, and Pd are arranged along an intermediate transfer belt 130. is there.

  In the image forming portion Pa, a yellow toner image is formed on the photosensitive drum 3 a and is primarily transferred to the intermediate transfer belt 130. In the image forming unit Pb, a magenta toner image is formed on the photosensitive drum 3 b and is primarily transferred to the intermediate transfer belt 130. In the image forming portions Pc and Pd, a cyan toner image and a black toner image are formed on the photosensitive drums 3c and 3d, respectively, and sequentially transferred onto the intermediate transfer belt 130.

  The recording material P is taken out from the recording material cassette 10 one by one and waits on the registration roller 12. The registration roller 12 feeds the recording material P to the secondary transfer portion T2 in time with the toner image on the intermediate transfer belt 130. The recording material P that has been transported through the secondary transfer portion T2 and secondarily transferred the four color toner images from the intermediate transfer belt 130 is transported to the fixing device 9 and is heated and pressed by the fixing device 9 to form a toner image. After fixing, the paper is discharged to a tray 7 outside the machine body.

  The image forming portions Pa, Pb, Pc, and Pd are configured substantially the same except that the color of toner used in the developing devices 1a, 1b, 1c, and 1d is different from yellow, magenta, cyan, and black. In the following, the image forming unit Pa will be described, and redundant description regarding the image forming units Pb, Pc, and Pd will be omitted.

  In the image forming portion Pa, a charging roller 2a, an exposure device 5a, a developing device 1a, a primary transfer roller 6a, and a drum cleaning device 4a are arranged around the photosensitive drum 3a. The photosensitive drum 3a has a photosensitive layer formed on the surface of an aluminum cylindrical material.

  The charging roller 2a charges the surface of the photosensitive drum 3a to a uniform potential. The exposure device 5a scans the laser beam and writes an electrostatic image of the image on the photosensitive drum 3a. The developing device 1a develops the electrostatic image and forms a toner image on the photosensitive drum 3a. The primary transfer roller 6 a is applied with a voltage to primarily transfer the toner image on the photosensitive drum 3 a to the intermediate transfer belt 130.

  The drum cleaning device 4a rubs the photosensitive drum 3a with a cleaning blade to collect the transfer residual toner attached to the photosensitive drum 3a by escaping from the transfer to the intermediate transfer belt 130. The belt cleaning device 15 collects the transfer residual toner attached to the intermediate transfer belt 130 by escaping from the transfer to the recording material at the secondary transfer portion T2.

<Example 1>
As shown in FIG. 2, the fixing roller 101, which is an example of a rotating body, rotates in contact with the recording material. An external heating belt 105, which is an example of a belt member, rotates in contact with the fixing roller 101 in order to perform thermal adjustment of the fixing roller 101. The first support roller 103 and the second support roller 104, which are an example of a plurality of support rotating bodies, stretch and support the external heating belt 105. The thermistor 123, which is an example of a temperature detection element, abuts on the external heating belt 105 and detects the temperature.

  As shown in FIG. 3, a holding frame 206 a that is an example of a first holding unit rotatably holds one end of the first support roller 103 and the second support roller 104. A holding frame 206b, which is an example of a second holding unit, rotatably holds the other ends of the first support roller 103 and the second support roller 104. An intermediate frame 208, which is an example of a support member, supports the holding frame 206a and the holding frame 206b so as to be relatively rotatable so as to form a twist angle with respect to the first support roller 103 and the second support roller 104.

  As shown in FIG. 7, the worm wheel 118 which is an example of the shift movement control mechanism controls the shift movement of the external heating belt 105 along the first support roller 103 and the second support roller 104. The worm wheel 118 rotates the intermediate frame 208 so as to form an intersection angle between the bus of the external heating belt 105 and the bus of the fixing roller 101. Photo interrupters 133 and 134, which are examples of detection means, detect the position of the external heating belt 105 along the first support roller 103 and the second support roller 104. The control unit 140, which is an example of a control unit, operates the worm wheel 118 based on the detection outputs of the photo interrupters 133 and 134 to control the lateral movement of the external heating belt 105.

  As shown in FIG. 15, the restricting portions 300A and 300B, which are examples of the limit structure, limit the maximum relative rotation angle of the holding frame 206a and the holding frame 206b to a predetermined angle, thereby making further relative rotation impossible. To do. As shown in FIG. 18, the predetermined angle (γ) is larger than the maximum relative rotation angle (βmax) of the holding frame 206a and the holding frame 206b that is generated in accordance with the control of the lateral movement of the external heating belt 105.

  As shown in FIG. 15, the bent portion 301a, which is an example of the first contact portion, extends along the first support roller 103 and the second support roller 104 from the holding frame 206a toward the holding frame 206b. The flat surface portion 302a, which is an example of the second contact portion, extends along the first support roller 103 and the second support roller 104 from the holding frame 206b toward the holding frame 206a. The bent portion 301a and the flat portion 302a are in a positional relationship that overlaps with the relative rotation of the holding frame 206a and the holding frame 206b. The bent portions 301a and 301b and the flat portions 302a and 302b are arranged one by one at a distance in the stretching direction of the external heating belt 105.

  As shown in FIG. 14, a plate spring 123m, which is an example of a beam member, has a thermistor 123a fixed to one end and the other end fixed to a holding frame 206a, and the thermistor 123a is attached to the external heating belt 105 by cantilever elastic deformation. Follow. The predetermined angle (γ) is smaller than the maximum relative rotation angle of the holding frame 206a and the holding frame 206b that can cause the thermistor 123a to follow the external heating belt 105 by cantilever elastic deformation of the leaf spring 123m.

(Fixing device)
FIG. 2 is an explanatory diagram of a configuration of the fixing device according to the first exemplary embodiment. As shown in FIG. 2, the fixing device 9 presses the pressure roller 102 against the fixing roller 101 to form a nip portion N of the recording material. The nip portion N sandwiches and conveys the recording material P carrying the unfixed toner K, melts the toner, and fixes the image on the recording material P.

  In the fixing roller 101, an elastic layer 101b is disposed on the outer peripheral surface of a cored bar 101a, and the surface of the elastic layer 101b is covered with a release layer 101c. The fixing roller 101 is driven by a driving mechanism 141 including a gear train (not shown), and rotates in the direction of arrow A at a process speed of 300 mm / sec.

  In the pressure roller 102, an elastic layer 102b is disposed on the outer peripheral surface of the cored bar 102a, and the surface of the elastic layer 102b is covered with a release layer 102c. The pressure roller 102 is driven by the drive mechanism 141 and rotates in the arrow B direction. The pressure roller 102 is driven by a pressure mechanism (not shown) using an eccentric cam and is brought into contact with and separated from the fixing roller 101. A pressure mechanism (not shown) presses the pressure roller 102 to the fixing roller 101 with a predetermined pressure, and forms a nip portion N between the fixing roller 101 and the pressure roller 102.

  The halogen heater 111 is non-rotatably disposed inside the cored bar 101 a of the fixing roller 101. The thermistor 121 is disposed in contact with the fixing roller 101 and detects the surface temperature of the fixing roller 101. The control unit 140 performs ON / OFF control of the halogen heater 111 according to the temperature detected by the thermistor 121 to maintain the surface temperature of the fixing roller 101 at a predetermined target temperature corresponding to the type of recording material.

  The halogen heater 112 is disposed in a non-rotating manner inside the cored bar 102 a of the pressure roller 102. The thermistor 122 is disposed in contact with the pressure roller 102 and detects the surface temperature of the pressure roller 102. The control unit 140 controls ON / OFF of the halogen heater 112 according to the temperature detected by the thermistor 122, and maintains the surface temperature of the pressure roller 102 at a predetermined target temperature.

(External heating belt)
As shown in FIG. 2, the image forming apparatus is required to have high productivity (number of printed sheets per unit time) even for a recording material having a large basis weight (weight per unit area) such as cardboard. In order to increase productivity with a recording material having a large basis weight, it is necessary to speed up the heat treatment in the fixing device 9. However, since a recording material having a large basis weight takes away a lot of heat, the amount of heat required for fixing becomes larger than that of a recording material having a low basis weight. Therefore, the fixing device 9 is arranged so that the external heating belt 105 can be brought into contact with / separated from the fixing roller 101. The external heating belt 105 increases the contact area for conducting heat from the first support roller 103 and the second support roller 104 to the fixing roller 101, and increases the heating efficiency of the fixing roller 101.

  The external heating belt 105 abuts on the outer peripheral surface of the fixing roller 101 to form a nip portion Ne and heats the fixing roller 101 externally. The external heating belt 105 has a base layer made of metal such as stainless steel or nickel, or a base layer made of resin such as polyimide. The surface of the base layer is covered with a heat-resistant sliding layer using a fluorine-based resin in order to prevent toner adhesion. The external heating belt 105 is frictionally driven with the rotation of the fixing roller 101 and is driven to rotate in the direction of arrow C.

  The first support roller 103 is made of a metal having high thermal conductivity such as aluminum, iron, and stainless steel. A halogen heater 113 is disposed non-rotatingly through the center of the first support roller 103. The thermistor 123 is in contact with the external heating belt 105 supported by the first support roller 103 and detects the temperature. The control unit 140 controls ON / OFF of the halogen heater 113 according to the temperature detected by the thermistor 123, and maintains the temperature of the first support roller 103 at a predetermined target temperature.

  The second support roller 104 is formed of a metal having high thermal conductivity such as aluminum, iron, and stainless steel. The halogen heater 114 is disposed non-rotatingly through the center of the second support roller 104. The thermistor 124 is in contact with the external heating belt 105 supported by the second support roller 104 and detects the temperature. The control unit 140 controls ON / OFF of the halogen heater 114 according to the temperature detected by the thermistor 124, and maintains the temperature of the second support roller 104 at a predetermined target temperature.

  The target temperature for temperature adjustment of the first support roller 103 and the second support roller 104 is set higher than the target temperature for temperature adjustment of the fixing roller 101. If the surface temperature of the first support roller 103 and the second support roller 104 is kept higher than the surface temperature of the fixing roller 101, heat can be supplied efficiently with respect to a decrease in the surface temperature of the fixing roller 101. It is. During continuous image formation of thick paper, the target temperature of the first support roller 103 and the second support roller 104 is set to 230 ° C. with respect to the target temperature of 165 ° C. of the fixing roller 101. The surface temperatures of the first support roller 103 and the second support roller 104 are kept 75 ° C. higher than the surface temperature of the fixing roller 101.

  The surface layer of the external heating belt 105 becomes dirty due to adhesion of foreign matters such as toner and paper powder transferred (offset) from the recording material. The cleaning roller 108 adsorbs foreign matters such as toner and paper dust to a silicon rubber layer provided on the surface. The cleaning roller 108 is pressed by the external heating belt 105 with a predetermined pressure and is rotated to clean the surface of the external heating belt 105.

  The fixing device 9 waits for the next image forming job in a state where the external heating belt 105 is separated from the fixing roller 101. When an image forming job is transmitted to the image forming apparatus, a preparation operation is started in each device in the image forming apparatus, and a heating operation is started in the fixing device 9. When the fixing roller 101, the pressure roller 102, and the external heating belt 105 reach their target temperatures in the heating operation, the external heating belt 105 is pressed against the fixing roller 101 and an image forming job is started. Thereafter, when the image forming job is completed, the external heating belt 105 is separated from the fixing roller 101 and is held until the next image forming start.

(Torsion angle of support roller)
FIG. 3 is an explanatory diagram of an external heating belt contact / separation mechanism. FIG. 4 is an explanatory view of a holding frame turning mechanism. FIG. 5 is an explanatory diagram of the crossing angle between the bus of the fixing roller and the bus of the external heating belt. FIG. 6 is an explanatory diagram of the effect of canceling the pressure difference due to the twist angle.

  As shown in FIG. 3, the external heating unit 150 stretches the external heating belt 105 around the first support roller 103 and the second support roller 104. Since the external heating belt 105 is rotatably supported by the first support roller 103 and the second support roller 104, it rotates following the rotation of the fixing roller 101.

  The external heating belt 105 can be brought into contact with / separated from the fixing roller 101 by the contact / separation mechanism 200. The contact / separation mechanism 200 also serves as a pressure contact mechanism that presses the first support roller 103 and the second support roller 104 against the fixing roller 101 via the external heating belt 105. The pressure frame 201 is rotatable with respect to the housing frame 9 f of the fixing device 9 about the support shaft 203.

  A pressure spring 204 is disposed between the rotating end of the pressure frame 201 and the housing frame 9 f of the fixing device 9. The pressure spring 204 pushes down the rotation end of the pressure frame 201 and biases the intermediate frame 208 toward the fixing roller 101. The intermediate frame 208 is rotatably supported with respect to the pressurizing frame 201 by a pair of intermediate rollers 210 disposed on the front side and the back side. In a state where the first support roller 103 and the second support roller 104 are in pressure contact with the fixing roller 101 via the external heating belt 105, the pressure spring 204 causes the upstream roller 103 and the second support roller 104 to have a total pressure of 392N (about 40 kgf). ).

  The pressure release cam 205 is in contact with the lower surface of the rotating end of the pressure frame 201. The control unit 140 controls the motor 210 to rotate the pressure release cam 205 about the rotation shaft 205a, thereby moving the rotation end of the pressure frame 201 up and down. When the pressure release cam 205 is separated from the pressure frame 201, the pressure spring 204 pushes down the rotating end of the pressure frame 201 and presses the external heating belt 105 against the fixing roller 101. When the pressure release cam 205 contracts the pressure spring 204 and pushes up the pressure frame 201, the external heating belt 105 is separated from the fixing roller 101.

  As shown in FIG. 4, the front ends of the first support roller 103 and the second support roller 104 are supported by the holding frame 206a. The front holding frame 206a is rotatably supported by the intermediate frame 208 by support shafts 207a and 207b. The holding frame 206a rotatably supports the front end portions of the first support roller 103 and the second support roller 104 via a heat insulating bush and a bearing (not shown). One end of the first support roller 103 and the second support roller 104 is rotatably supported by a bearing (not shown) fixed to the holding frame 206a. The holding frame 206a is rotatably supported by shafts 207a and 207b installed on the intermediate frame 208.

  The inner ends of the first support roller 103 and the second support roller 104 are supported by the holding frame 206b. The rear holding frame 206b is rotatably supported by the intermediate frame 208 by support shafts 207c and 207d. The holding frame 206b rotatably supports end portions of the first support roller 103 and the second support roller 104 via a heat insulating bush and a bearing (not shown). The other ends of the first support roller 103 and the second support roller 104 are rotatably supported by a bearing (not shown) fixed to the holding frame 206b. The holding frame 206b is rotatably supported by shafts 207c and 207d installed on the intermediate frame 208.

  As shown in FIG. 4, pressure springs 204 a and 204 b are disposed at both ends of the pressure frame 201 in the longitudinal direction. The pressure spring 204 brings the external heating belt 105 into contact with the outer peripheral surface of the fixing roller 101 with a predetermined pressure via the first support roller 103 and the second support roller 104. A straight line connecting the support shafts 207a, 207b, 207c, and 207d and the center of the fixing roller 101 is a straight line connecting the centers of the first support roller 103 and the second support roller 104 with the external heating belt 105 in close contact with the fixing roller 101. This is a vertical bisector.

  As shown in FIG. 5, when the bus of the external heating belt 105 and the bus of the fixing roller 101 have an intersection angle θ, one of the first support roller 103 and the second support roller 104 precedes at the end on the back side. Then, pressurization of the fixing roller 101 is started. At the same time, at the end on the near side, the other of the first support roller 103 and the second support roller 104 starts to press the fixing roller 101 in advance. One end of the first support roller 103 (second support roller 104) in the longitudinal direction bites into the fixing roller 101, and the other end separates from the fixing roller 101. For this reason, the distribution of the nip pressure between the fixing roller 101 and the external heating belt 105 in the longitudinal direction of the fixing roller 101 becomes non-uniform.

  As shown in FIG. 6 (a), the pressure difference between the first support roller 103 and the second support roller 104 causes the front holding frame 206a and the rear holding frame 206b to autonomously rotate. The pressure difference between the first support roller 103 and the second support roller 104 is canceled out. The holding frame 206a on the near side and the holding frame 206b on the back side rotate relative to each other, and the first support roller 103 and the second support roller 104 are positioned at a twisted position corresponding to the curved surface of the fixing roller 101. Since the relative twist angle between the first support roller 103 and the second support roller 104 is free, the postures of the first support roller 103 and the second support roller 104 are autonomously moved to the twist position corresponding to the curved surface of the fixing roller 101. The external heating belt 105 comes into close contact with the fixing roller 101.

  As shown in FIG. 6B, on the front side, the holding frame (206a) rotates about the support shafts 207a and 207b to cancel the pressure difference between the first support roller 103 and the second support roller 104. . As shown in FIG. 6C, on the back side, the holding frame (206b) rotates about the support shafts 207c and 207d to cancel the pressure difference between the first support roller 103 and the second support roller 104. . For this reason, the distribution of the nip pressure between the fixing roller 101 and the external heating belt 105 when the crossing angle θ is changed in accordance with the control of the lateral movement of the external heating belt 105 becomes uniform.

  As a result of both the first support roller 103 and the second support roller 104 being evenly pressed against the fixing roller 101, the first support roller 103 and the second support roller 104 are passed through the external heating belt 105 on the front side and the back side. Thus, sufficient external heating is performed on the fixing roller 101.

(Steering mechanism)
FIG. 7 is an explanatory view of the steering mechanism of the external heating belt. FIG. 8 is an explanatory diagram of a drive unit of the steering mechanism. FIG. 9 is an enlarged view of the drive unit of the steering mechanism.

  As shown in FIG. 2, the fixing device 9 rotates the external heating unit 150 while keeping the positional relationship between the first support roller 103 and the second support roller 104 constant, and the first support roller 103 and the second support roller. The lateral movement of the external heating belt 105 along 104 is controlled.

  As shown in FIG. 5, when the external heating belt 105 and the fixing roller 101 are in contact with each other at an intersection angle θ, the first support roller 103 and the second support roller are rotated with respect to the external heating belt 105 by the rotation of the fixing roller 101. A shifting force along 104 is generated. Using this principle, the fixing device 9 intentionally changes the crossing angle θ to forcibly set the direction of the lateral movement of the external heating belt 105.

  The external heating belt 105 moves along the first support roller 103 and the second support roller 104 during the rotation operation. The cause of the shift is the shift in parallelism between the first support roller 103 and the second support roller 104, the above-described crossing angle θ, and the like.

  As shown in FIG. 7, a rotation shaft 209 is arranged in the normal direction to the contact surface where the fixing roller 101 and the external heating belt 105 are in contact with each other. The rotation shaft 209 is a rotation center that changes the intersection angle θ between the external heating belt 105 and the fixing roller 101. Since the rotation shaft 209 is disposed at the center of the external heating unit 150, the nip pressure balance between the front side and the back side in the longitudinal direction of the fixing roller 101 is stabilized.

  The controller 140 integrally tilts the first support roller 103 and the second support roller 104 about the rotation shaft 209 to change the intersection angle θ between the bus of the external heating belt 105 and the bus of the fixing roller 101. Thus, the direction of the external heating belt 105 is controlled. The controller 140 forcibly changes the crossing angle θ between the bus of the external heating belt 105 and the bus of the fixing roller 101 from the outside, reverses the shift of the external heating belt 105, and shifts the external heating belt 105. Keep the range within the predetermined range.

  Both ends of the support shaft 203 of the pressure frame 201 are fixed to the main body side plate 202. The intermediate frame 208 and the external heating belt 105 can be integrally rotated with respect to the pressure frame 201 around the rotation shaft 209. The support shaft 207a fixed to the intermediate frame 208 is held with a clearance with the main body side plate 202, and can move in the directions of arrows H and J within the clearance range as the arm portion 118a moves.

  A fan-shaped worm wheel 118 that can rotate around the rotation shaft 119 meshes with the worm gear 120. When the motor 125 rotates in the forward direction and the worm wheel 118 rotates in the arrow G direction, the arm portion 118a moves in the arrow H direction and moves the support shaft 207a in the arrow H direction. When the motor 125 rotates in the reverse direction and the worm wheel 118 rotates in the direction of arrow I, the arm portion 118a moves in the direction of arrow J and moves the support shaft 207a in the direction of arrow J (see FIGS. 7 and 8). .

  When the front side of the intermediate frame 208 moves in the direction of arrow H or J, the first support roller 103 and the second support roller 104 rotate around the rotation shaft 209, and the fixing roller 101, the first support roller 103, An intersection angle θ is set between the second support rollers 104. There is a relationship between the crossing angle θ between the fixing roller 101 and the external heating belt 105 and the shifting speed of the external heating belt 105. The shifting force of the external heating belt 105 changes according to the amount of movement of the arm portion 118a, and the direction and shifting speed of the external heating belt 105 along the first support roller 103 and the second support roller 104 are controlled. .

  When the support shaft 207a moves in the H direction from the point of zero offset force, the offset force that moves the external heating belt 105 to the back side (in the arrow M direction) of the fixing roller 101 increases. When the support shaft 207a moves in the J direction from the point of zero offset force, the offset force that moves the external heating belt 105 toward the front side (arrow L direction) of the fixing roller 101 increases. Thus, by moving the support shaft 207a in the directions of arrows H and J, the direction in which the external heating belt 105 approaches can be controlled in the directions of arrows M and L.

  In the present embodiment, the support shaft 207 a is fixed by the worm wheel 118 with the position where the external heating unit 150 is mounted so as to be parallel to the fixing roller 101 as the home position. The home position is detected by the photo interrupter 135 attached to the worm wheel 118.

  When the fixing roller 101 rotates, the external heating belt 105 is driven to rotate, and the external heating belt 105 approaches either the front side or the back side in the longitudinal direction. The controller 140 shifts the position of the support shaft 207a so that a force is applied in a direction opposite to the direction in which the external heating belt 105 approaches.

(Belt deviation detection sensor)
FIG. 10 is an explanatory diagram of the arrangement of the belt deviation amount detection sensors. FIG. 11 is an explanatory diagram of the relationship between the belt shift direction and the rotation direction of the sensor flag. As shown in FIG. 10B, the arm 129 and the roller 128 rotate together around the rotation axis 136. The sensor flag 132 rotates around the rotation shaft 137.

  As shown in FIG. 10A, the arm 129 and the sensor flag 132 are engaged by a link portion 138 to transmit rotation. The roller 128 is in contact with the belt edge of the external heating belt 105. The torsion spring 131 applies torque to the arm 129 to urge the roller 128 in the direction of arrow Q.

  Therefore, as shown in FIG. 10B, when the external heating belt 105 is moved in the arrow Q direction, the link portion 138 moves in the arrow P direction. When the external heating belt 105 approaches the arrow R direction, the link portion 138 moves in the arrow O direction.

  As shown in FIG. 11A, photointerrupters 133 and 134 are arranged along the sensor flag 132. The photo interrupters 133 and 134 detect the four edges of the two slits formed in the sensor flag 132 and invert the outputs. Corresponding positions of the external heating belt 105 are defined in correspondence with the four edges of the sensor flag 132. As an example, the photointerrupters 132 and 133 are arranged so that the external heating belt 105 repeats shifting with an amplitude of 5 mm. When the external heating belt 105 approaches the arrow R direction, the arm 129 rotates in the arrow S direction, the sensor flag 132 rotates in the arrow T direction, the photo interrupter 133 is turned off, and the photo interrupter 134 is turned on.

  As shown in FIG. 11B, when the external heating belt 105 approaches the arrow Q direction, the arm 129 rotates in the arrow U direction, the sensor flag 132 rotates in the arrow V direction, and the photo interrupter 133 is turned on. Then, the photo interrupter 134 is turned off.

(Comparative example)
FIG. 12 is an explanatory diagram of a fixing device of a comparative example.

  As shown in FIG. 7, the external heating unit 150 supplies the amount of heat directly to the surface of the fixing roller 101 by bringing the external heating belt 105 into contact therewith. The external heating unit 150 controls the shift of the external heating belt 105 by rotating around the rotation shaft 209 and changing the crossing angle θ between the bus of the external heating belt 105 and the bus of the fixing roller 101. In addition, the holding frames 206a and 206b rotate relative to the support shafts 207a, 207b, 207c, and 207d as the external heating belt 105 moves, and the first support roller 103 and the second support roller 104 A twist angle is formed between the two. Thereby, the nip pressure distribution with the fixing roller 101 along the first support roller 103 and the second support roller 104 is made uniform on the front side and the back side in the longitudinal direction.

  Here, in the case where the twist angle of the first support roller 103 and the second support roller 104 can be set to be unlimited, the twist angle is increased when the external heating unit 150 is assembled or when the external heating unit 150 is lifted alone. It can be excessive.

  As shown in FIG. 12A, the surface temperature of the external heating belt 105 is detected by a thermistor 123 (123a, 123b) that contacts the contact area between the first support roller 103 and the external heating belt 105. And when the twist angle between the first support roller 103 and the second support roller 104 becomes excessive, the distance between the thermistors 123a, 123b and the external heating belt 105 becomes closer than expected when it occurs during control, To leave.

  As shown in FIG. 12B, the effect is particularly great with respect to the thermistor 123a arranged near the center in the longitudinal direction in order to detect the temperature at the center of the external heating belt 105. If the leaf spring 123m that supports the thermistor 123a is plastically deformed in accordance with the torsion angle between the first support roller 103 and the second support roller 104, the thermistor 123a may not contact the surface of the external heating belt 105.

  Therefore, in the following embodiment, a limiter is provided at the twist angle between the first support roller 103 and the second support roller 104 to solve the problem of the comparative example. The limiter regulates the twist angle between the first support roller 103 and the second support roller 104, so that the displacement amount of the plate spring 123m of the thermistor 123a that detects the surface temperature of the external heating belt 105 by contacting the external heating belt 105 is reduced. It is reduced.

(Characteristic configuration of Example 1)
FIG. 13 is an explanatory diagram of the arrangement of the restricting portions in the first embodiment. FIG. 14 is an explanatory diagram of the operation of the holding frame. FIG. 15 is a perspective view of the restricting portion. FIG. 16 is an explanatory diagram of the operation of the restricting unit.

  As shown in FIG. 13, the external heating unit 150 is divided into an upper portion 150U and a lower portion 150D. The upper portion 150U rotates the intermediate frame 208 around the rotation shaft 209 with respect to the pressure frame 201. The lower portion 150D is supported by being rotatably suspended by shafts 207a, 207b, 207c, and 207d installed on the intermediate frame 208. The lower portion 150D rotatably supports one end portions of the first support roller 103 and the second support roller 104 by the holding frame 206a, and the other end portion of the first support roller 103 and the second support roller 104 by the holding frame 206b. Support for rotation.

  As shown in FIG. 14, the lower portion 150D rotates the holding frame 206a and the holding frame 206b relatively to twist the holding frame 206a and the holding frame 206b. Thereby, a torsion angle is set between the first support roller 103 and the second support roller 104, and the pressure distribution in the nip portion with the fixing roller 101 in the longitudinal direction of the external heating belt 105 is set as shown in FIG. Will be leveled evenly autonomously.

  As shown in FIG. 13, restricting portions 300A and 300B are formed on the holding frames 206a and 206b. The restricting units 300A and 300B limit the torsion angle between the first support roller 103 and the second support roller 104 by limiting the relative rotation angle between the holding frame 206a and the holding frame 206b.

  As shown in FIG. 15, the holding frame 206a is formed with two bent portions 301a and 301b bent in two stages at the center end portion with the shaft 207b interposed therebetween. The holding frame 206b is formed with two flat portions 302a and 302b protruding from the central end portion with the shaft 207c interposed therebetween. In the restricting portion 300A, the bent portion 301a formed on the holding frame 206a extends to above the flat portion 302a formed on the holding frame 206b, and the bent portion 301a and the flat portion 302a overlap in the longitudinal direction. In the restricting portion 300B, the bent portion 301b formed on the holding frame 206a extends to above the flat portion 302b formed on the holding frame 206b, and the bent portion 301b and the flat portion 302b overlap in the longitudinal direction.

  As shown in FIG. 16A, when the holding frame 206b rotates relative to the holding frame 206a in the direction of arrow A, the flat portion 302b of the holding frame 206b comes into contact with the bent portion 301b of the holding frame 206a. The above relative rotation is restricted.

  As shown in FIG. 16B, when the holding frame 206b rotates relative to the holding frame 206a in the direction of the arrow B, the flat portion 302a of the holding frame 206b comes into contact with the bent portion 301a of the holding frame 206a. The above relative rotation is restricted.

  In this way, the bent portions 301a and 301b formed on the holding frame 206a and the flat portions 302a and 302b formed on the holding frame 206b are in contact with each other, so that the gap between the first support roller 103 and the second support roller 104 is between them. An excessive twist angle is not generated.

(Relative rotation angle of holding frame)
FIG. 17 is an explanatory diagram of the relative rotation angle of the holding frame. FIG. 18 is an explanatory diagram of a restriction angle of the relative rotation of the holding frame. FIG. 19 is an explanatory diagram of the effect of the first embodiment.

  As shown in FIG. 17A, the first support roller 103 and the second support roller 104 are changed by changing the crossing angle of the bus of the external heating belt 105 with respect to the bus of the fixing roller 101 around the rotation shaft 209. The lateral movement of the external heating belt 105 along the axis is controlled. Let α be the crossing angle of the fixing roller 101 and the external heating belt 105 in the control of the lateral movement of the external heating belt 105. The intersection angle α is controlled in accordance with a change in the shifting speed of the external heating belt 105, a change in the shifting position, and the like. If the crossing angle α is set to be equal to or less than a certain upper limit value and the shift movement cannot be controlled even with the upper limit value, it is determined that there is a problem with the external heating unit 150 and an error message is displayed. In the first embodiment, the upper limit value αmax of the intersection angle α is set to 2 degrees.

  As shown in FIG. 17B, when the crossing angle α between the external heating belt 105 and the fixing roller 101 is changed, the first support roller 103 and the second support roller 104 that stretch the external heating belt 105 are twisted. The positional relationship is Accordingly, the relative rotation angle formed by the holding frame 206a and the holding frame 206b is β. The relative rotation angle β between the holding frame 206a and the holding frame 206b when the crossing angle of the bus of the external heating belt 105 with respect to the bus of the fixing roller 101 is the upper limit αmax is set to the upper limit βmax. In the first embodiment, the upper limit value βmax is set to 6 degrees.

As shown in FIG. 18, the relative rotation angle between the holding frame 206a and the holding frame 206b, which is regulated by contact between the bent portion 301b of the holding frame 206a and the flat portion 302b of the holding frame 206b, is γ. In Example 1, the relationship between the relative rotation angle γ and the upper limit value βmax was set as follows.
γ ≧ βmax

  Since the angle γ varies depending on the component tolerance, it is desirable to design with γ> βmax as a design value. When the relative rotation angle γ is smaller than the upper limit value βmax, the twist angles of the first support roller 103 and the second support roller 104 are insufficient when the lateral movement of the external heating belt 105 is controlled, and the external heating belt 105 and the fixing roller 101 are moved. The nip pressure distribution in the longitudinal direction becomes non-uniform.

  In Example 1, the angle γ was set to 8 degrees, which is larger than the upper limit value βmax of 6 degrees. For this reason, when the lateral movement of the external heating belt 105 is controlled, the longitudinal nip pressure distribution between the external heating belt 105 and the fixing roller 101 is not affected. When the external heating belt 105 is assembled or when the external heating unit 150 is lifted alone, the first support roller 103 and the second support roller 104 that suspend the external heating belt 105 are not greatly twisted.

  As shown in FIG. 19A, in Comparative Example 1, since the distance between the external heating belt 105 and the thermistor 123a is large as the first support roller 103 is twisted, the leaf spring 123m is bent and plastically deformed. there's a possibility that. As shown in FIG. 19B, in Example 1, since the change in the distance between the external heating belt 105 and the thermistor 123a is restricted to a small extent as the first support roller 103 is twisted, the leaf spring 123m is bent. Therefore, plastic deformation is not necessary.

  According to the first embodiment, when the crossing angle θ between the fixing roller 101 and the external heating belt 105 is changed to control the shift of the external heating belt 105, the required relative rotation angle between the holding frame 206a and the holding frame 206b is set. Sufficiently secured. The distribution of the nip pressure with the fixing roller in the longitudinal direction of the external heating belt 105 can be kept uniform without affecting the control of the lateral movement of the external heating belt 105. In addition, the relative rotation angle between the holding frame 206a and the holding frame 206b is regulated so that the torsion angles of the first support roller 103 and the second support roller 104 are within an allowable range, so that the displacement of the plate spring 123m of the thermistor 123a The amount is reduced.

  According to the first embodiment, when the external heating belt 105 is replaced or when the external heating unit 150 is lifted up alone, the first support roller 103 and the second support roller 104 do not have to be greatly twisted.

  In the first embodiment, the rotation shaft 209 is provided in the external heating unit 150 and the crossing angle with the fixing roller 101 is changed to control the shift of the external heating belt 105. The first support roller 103 that stretches the external heating belt 105 and the holding frames 206 a and 206 b that hold the ends of the second support roller 104 are twisted.

  However, since the twist is restricted by an angle larger than the maximum value of the twist angle used in the shift control, the temperature is detected by contacting the surface of the external heating belt 105 without affecting the shift control of the external heating belt 105. The amount of displacement of the thermistor 123a can be regulated. For this reason, when the external heating belt 105 is assembled, the first support roller 103 and the second support roller 104 are not greatly twisted, and the thermistor 123a that contacts the surface of the external heating belt 105 and detects the temperature is not greatly displaced. .

<Example 2>
FIG. 20 is an explanatory diagram of the arrangement of the restricting portions in the second embodiment. FIG. 21 is an explanatory diagram of the thermistor arrangement in the second embodiment. FIG. 22 is an explanatory diagram of a structure for preventing rotation of the sensor support shaft with respect to the holding frame. FIG. 23 is an explanatory view at the time of relative rotation of the holding frame. FIG. 24 is an explanatory diagram of the operation of the restriction unit in the second embodiment. As shown in FIG. 21, the sensor support shaft 303, which is an example of a both-supported beam member, is arranged so as to span between the holding frame 206a and the holding frame 206b. The sensor support shaft 303 forms a twist angle with respect to the first support roller 103 and the second support roller 104 as the holding frame 206a and the holding frame 206b rotate relative to each other.

  As shown in FIG. 12, in Example 1, when the holding frames 206a and 206b are relatively rotated and are in a twisted positional relationship, the distance between the horizontal portion of the holding frame 206a and the surface of the first support roller 103 is large. fluctuate. For this reason, the leaf spring 123m whose root is fixed to the horizontal portion of the holding frame 206a needs to absorb a large amount of displacement of the thermistor 123a by deformation.

  As shown in FIG. 20, in Example 2, when the holding frames 206a and 206b are relatively rotated and are in a torsional positional relationship, the root of the leaf spring 123m moves up and down, and the root of the leaf spring 123m and the thermistor 123a. Reduce the amount of displacement. For this reason, the displacement amount of the distance between the thermistors 123a and 123b and the surface of the first support roller 103 is small when the first support roller 103 and the second support roller 104 are in a twisted positional relationship.

  As shown in FIG. 20, in the second embodiment, a sensor support shaft 303 is arranged in parallel with the first support roller 103 between the holding frame 206 a and the holding frame 206 b, and the sensor is supported in parallel with the second support roller 104. An axis 304 is arranged. Then, the thermistors 123a and 123b are arranged to be supported by the sensor support shaft 303, and the thermistors 124a and 124b are arranged to be supported by the sensor support shaft 304.

  A holding frame 206 a that rotatably holds one end of the first support roller 103 and the second support roller 104 is rotatably supported by a shaft 207 a disposed on the intermediate frame 208. Holding frames 206a and 206b that rotatably hold the other ends of the first support roller 103 and the second support roller 104 are rotatably supported by a shaft 207b disposed on the intermediate frame 208.

  As shown in FIG. 21, the sensor support shafts 303 and 304 are disposed so as to connect the holding frame 206a and the holding frame 206b and penetrate the holding frame 206a and the holding frame 206b. The base sides of the leaf springs 123m and 123n are fixed to the sensor support shaft 303, and the thermistors 123a and 123b are fixed to the distal ends of the leaf springs 123m and 123n. The base sides of the leaf springs 124m and 124n are fixed to the sensor support shaft 304, and the thermistors 124a and 124b are fixed to the distal ends of the leaf springs 124m and 124n.

  As shown in FIG. 22, the end portions of the sensor support shafts 303 and 304 inserted into the holding frame 206a are cut into a D shape, and the rotation is restricted with respect to the holding frame 206a. The end portions of the sensor support shafts 303 and 304 are rotatable with respect to the holding frame 206b. The sensor support shafts 303 and 304 are fitted with retaining rings 305 at positions protruding from the holding frames 206a and 206b with respect to the holding frames 206a and 206b.

  As shown in FIG. 23A, the holding frames 206a and 206b rotate relative to each other in accordance with the control of the lateral movement of the external heating belt 105, so that the first support roller 103 and the second support roller 104 are in a twisted positional relationship. Become. At the same time, the sensor support shafts 303 and 304 are also in a twisted positional relationship, and the first support roller 103 and the sensor support shaft 303 are maintained in a substantially parallel positional relationship, and the second support roller 104 and the sensor support shaft are maintained. 304 maintains a substantially parallel positional relationship. For this reason, the displacement amount of the distance between the thermistors 123a and 123b and the first support roller 103 due to the relative rotation of the holding frame 206a and the holding frame 206b is smaller than that in the first embodiment. At the same time, the displacement amount of the distance between the thermistors 124a and 124b and the second support roller 104 due to the relative rotation of the holding frame 206a and the holding frame 206b is also smaller than that in the first embodiment.

  As shown in FIGS. 23B and 23C, even if the first support roller 103 and the second support roller 104 are twisted, the sensor support shaft 303 and the first support roller 103 are parallel to each other. The relationship and the parallel positional relationship between the sensor support shaft 304 and the second support roller 104 do not change. Since the sensor support shafts 303 and 304 are prevented from coming off from the holding frames 206a and 206b, the first support roller 103 and the sensor support shaft 303 are twisted in the same direction, and the second support roller 104 and the sensor support shaft 304 are twisted. This is because it twists in the same direction.

  Accordingly, the thermistors 123a, 123b, 124a, 124b attached to the sensor support shafts 303, 304 via the leaf springs 123m, 123n, 124m, 124n are in contact positions with the first support roller 103 and the second support roller 104. The shift is small. The plastic deformation of the leaf springs 123m, 123n, 124m, and 124n accompanying the shift control of the external heating belt 105 is less likely to occur than in the first embodiment.

  However, also in the second embodiment, when the external heating unit 150 is assembled or when the external heating unit 150 is lifted up alone, the first support roller 103 and the second support roller 104 are largely twisted, and the leaf spring 123m is plastic. There is a possibility of deformation.

  Therefore, as shown in FIG. 20, plane portions 305a and 305b are arranged on the front side of the intermediate frame 208 to limit the rotation angle of the holding frame 206a. Flat portions 306a and 306b are arranged on the back side of the intermediate frame 208 to limit the rotation angle of the holding frame 206b.

  As shown in FIG. 24, on the front side, the flat portions 305a and 305b fixed to the intermediate frame 208 abut against the holding frame 206a, and the twist angle of the holding frame 206a with respect to the intermediate frame 208 is restricted within a predetermined range. On the back side, the flat portions 306a and 306b fixed to the intermediate frame 208 abut against the holding frame 206b, and the twist angle of the holding frame 206b with respect to the intermediate frame 208 is restricted within a predetermined range. As in the first embodiment, the predetermined range of each twist angle is set to an angle slightly larger than the twist angle generated by the control of the shift of the external heating belt 105 so as not to hinder the control of the shift. ing. FIG. 24 shows the holding frame 206a, but the holding frame 206b has the same configuration.

  In the second embodiment, since the displacement amounts of the thermistors 123a, 123b, 124a, and 124b are smaller than those in the first embodiment, the reproducibility of temperature detection by the thermistors 123a, 123b, 124a, and 124b is increased. In the second embodiment, as compared with the first embodiment, the torsion of the external heating unit 150 is somewhat inhibited by the sensor support shafts 303 and 304, but the temperature detection error due to the plastic deformation of the leaf springs 123m, 123n, 124m, and 124n. Can be greatly reduced.

<Example 3>
FIG. 25 is an explanatory diagram of a restriction unit according to the third embodiment. As shown in FIG. 25, the configuration for limiting the relative rotation angle of the holding frames 206a and 206b may be arranged in one place.

  As long as the maximum relative rotation angle between the first holding part and the second holding part is regulated to a predetermined angle so that an excessive burden is not applied to the predetermined part, the present invention can partially or entirely configure the configuration of the embodiment. However, another embodiment in which the alternative configuration is replaced can also be implemented.

  Therefore, the heating means of the rotating body (roller member or belt member) is not limited to the halogen heater. An induction heating layer may be provided on the rotating body and the belt member, and induction heating may be performed with an alternating magnetic flux. The belt member in the present invention is not limited to the heating application of the rotating body. It can also be implemented in a soaking application that averages the temperature distribution in the rotation axis direction of the rotating body and a cooling application that promotes cooling of the rotating body. The rotating body is not limited to the fixing roller, and may be a pressure roller that heats the back surface of the image surface of the recording material.

  In addition to the fixing device, the image heating device includes a surface heating device that adjusts the gloss and surface properties of a semi-fixed or fixed image. Also included is a decurling device for the recording material on which the fixed image is formed. In addition to being incorporated in the image forming apparatus, the image heating apparatus can be implemented as a single apparatus or component unit that is installed and operated independently. The image forming apparatus can be implemented without distinction between monochrome / full color, sheet-fed type / recording material conveyance type / intermediate transfer type, toner image forming method, and transfer method. The present invention can be implemented in image forming apparatuses for various uses such as a printer, various printing machines, a copying machine, a FAX, and a multifunction machine, in addition to necessary equipment, equipment, and a housing structure.

9 Fixing device, 11 Secondary transfer roller 101 Fixing roller, 102 Pressure roller 103 First support roller, 104 Second support roller 105 External heating belt, 108 Cleaning rollers 111, 112, 113, 114 Halogen heater 117 Pressure arm, 118 Worm wheel, 125 Motor 130 Intermediate transfer belt, 133, 134, 135 Photo interrupter 150 External heating unit, 201 Pressure frame, 204 Pressure spring 205 Pressure release cam, 206 Holding frame 207 Axis, 208 Intermediate frame, 209 Rotation axis 211 Rotation restricting member, 301 Bending portion, 302 Planar portion 303, 304 Sensor support shaft K Toner, P Recording material, Pa, Pb, Pc, Pd Image forming portion

Claims (7)

A rotating body that rotates in contact with the recording material;
A belt member that rotates in contact with the fixing roller 101 in order to perform thermal adjustment of the fixing roller 101;
A plurality of support rotators for supporting the belt member by stretching;
A first holding part for rotatably holding one end part of the plurality of support rotating bodies;
A second holding portion for rotatably holding the other end portions of the plurality of support rotating bodies;
A support member that rotatably supports the first holding portion and the second holding portion so as to form a twist angle in the plurality of support rotating bodies;
A lateral movement that controls the lateral movement of the belt member along the plurality of support rotating bodies by rotating the support member so as to form an intersection angle between the bus line of the belt member and the bus line of the fixing roller 101. A control mechanism;
An image heating apparatus, comprising: a limit structure that limits a maximum relative rotation angle between the first holding unit and the second holding unit to a predetermined angle and makes further relative rotation impossible.   2. The image heating according to claim 1, wherein the predetermined angle is larger than a maximum relative rotation angle of the first holding part and the second holding part that is generated in accordance with control of the shift movement of the belt member. apparatus. A temperature detecting element for detecting the temperature in contact with the belt member;
A beam member for fixing the temperature detection element at one end and fixing the other end to the first holding portion, and allowing the temperature detection element to follow the belt member by cantilever elastic deformation;
The predetermined angle is smaller than a maximum relative rotation angle of the first holding part and the second holding part that can cause the temperature detection element to follow the belt member by elastic deformation of the beam member. The image heating apparatus according to claim 2. A temperature detecting element for detecting the temperature in contact with the belt member;
The first holding part and the second holding part are formed between the first holding part and the second holding part so as to form a twist angle with respect to the plurality of support rotating bodies as the first holding part and the second holding part rotate relative to each other. A doubly-supported beam member,
A beam member for fixing the temperature detection element at one end and fixing the other end to the both-end supported beam member, and allowing the temperature detection element to follow the belt member by cantilever elastic deformation;
The predetermined angle is smaller than a maximum relative rotation angle of the first holding part and the second holding part that can cause the temperature detection element to follow the belt member by elastic deformation of the beam member. The image heating apparatus according to claim 2. The limit structure includes a first abutting portion extending along the support rotating body from the first holding portion toward the second holding portion, and from the second holding portion toward the first holding portion. A second abutting portion extended along the support rotating body,
5. The positional relationship in which the first contact portion and the second contact portion overlap with each other as the first holding portion and the second holding portion rotate relative to each other. The image heating apparatus according to claim 1.   The image heating apparatus according to claim 5, wherein the first contact portion and the second contact portion are arranged one by one at a distance in the stretching direction of the belt member. Detecting means for detecting a shift position of the belt member along the plurality of support rotating bodies;
7. The control unit according to claim 1, further comprising: a control unit configured to operate the shift movement control mechanism based on a detection output of the detection unit to control the shift movement of the belt member. Image heating device.

Images